[Gluster-users] 3.7.16 with sharding corrupts VMDK files when adding and removing bricks

[Krutika Dhananjay]

Yes. I apologise for the delay.

Disabling sharding would knock the translator itself off the client stack,
and
being that sharding is the actual (and the only) translator that has the
knowledge of how to interpret sharded files, and how to aggregate them,
removing the translator from the stack will make all shards start to appear
like
isolated files with no way to interpret the correlation between the
individual pieces.

The only way to fix it is to have sharding be part of the graph *even* if
disabled,
except that in this case, its job should be confined to aggregating the
already
sharded files during reads but NOT shard new files that are created, since
it is
supposed to "act" disabled. This is a slightly bigger change and this is
why I had
suggested the workaround at
https://bugzilla.redhat.com/show_bug.cgi?id=1355846#c1
back then.

FWIW, the documentation [1] does explain how to disable sharding the right
way and has been in existence ever since sharding was first released in
3.7.0.

[1] - http://staged-gluster-docs.readthedocs.io/en/release3.7.
0beta1/Features/shard/

-Krutika



On Mon, Nov 14, 2016 at 9:08 PM, Gandalf Corvotempesta <
gandalf.corvotempesta at gmail.com> wrote:

> 2016-11-14 15:54 GMT+01:00 Niels de Vos <ndevos at redhat.com>:
> > Obviously this is unacceptible for versions that have sharding as a
> > functional (not experimental) feature. All supported features are
> > expected to function without major problems (like corruption) for all
> > standard Gluster operations. Add-brick/replace-brick are surely such
> > Gluster operations.
>
> Is sharding an experimental feature even in 3.8 ?
> Because in 3.8 announcement, it's declared stable:
> http://blog.gluster.org/2016/06/glusterfs-3-8-released/
> "Sharding is now stable for VM image storage. "
>
> > FWIW sharding has several open bugs (like any other component), but it
> > is not immediately clear to me if the problem reported in this email is
> > in Bugzilla yet. These are the bugs that are expected to get fixed in
> > upcoming minor releases:
> >   https://bugzilla.redhat.com/buglist.cgi?component=
> sharding&f1=bug_status&f2=version&o1=notequals&o2=
> notequals&product=GlusterFS&query_format=advanced&v1=CLOSED&v2=mainline
>
> My issue with sharding was reported in bugzilla on 2016-07-12
> 4 months for a IMHO, critical bug.
>
> If you disable sharding on a sharded volume with existing shared data,
> you corrupt every existing file.
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